This invention relates generally to agricultural implements, and more specifically to structure for accurately determining and controlling the planting or tilling depth of such implements.
The depth of penetration of the tools on planting and tillage implements must be carefully controlled to achieve optimum productivity. Numerous factors such as changing soil conditions, implement weight, leakage in the depth-control cylinders and tire flex can cause changes in the operating depth of an implement. As soil moisture and soil consistency change, tool penetration can vary over a substantial range for a given wheel control cylinder setting. In addition, when fertilizer and/or seed are being metered from a hopper carried on the implement frame, soil penetration will change with the change in the weight of the materials carried by the hopper. If a depth-control cylinder leaks, the operator may be required to constantly adjust the cylinder to compensate for the loss and maintain a constant depth of penetration. On multiple-section implements which are hinged for flexing about generally fore-and-aft pivotal axes, the depth of penetration is commonly controlled by series-connected cylinders or by interconnected rockshafts. Depth can vary from section to section because of cylinder leakage in a series-cylinder system or because of torsional wind-up of the rockshaft of the rockshaft-connected system. On some implements, a hopper is carried only on one of the sections, usually the center section, and as the weight of the material in the hopper changes, the relative depths of penetration of the different sections will also change.
To overcome these and other problems associated with the many changing conditions which can affect implement frame height and the depth of penetration of the tools carried by the implement frame, numerous depth-sensing and depth-control devices have been devised. Some of these devices utilize a single depth-gauging wheel connected at one location along the width of the implement frame. In rough terrain, there is considerable variation between the wheel position of this type of sensor and the actual machine depth, particularly if the sensor wheel is positioned in a furrow or on a ridge. Surface irregularities can adversely affect the accuracy of these devices. Usually such devices are positioned so that the depth-gauging wheel rides on the untilled soil in front of the machine, and therefore the device cannot provide an accurate indication of the depth of the tilled soil. Devices such as shown in U.S. Pat. No. 4,355,688 utilize a wheel which rides over the tilled soil and provide some improvement in depth sensing. To provide a better average of implement frame height, more than one depth-control wheel can be utilized to provide depth indications, and the indications can be averaged. The multiple devices are relatively expensive and bulky, and in certain situations still do not provide a good indication of the average frame height.
Other depth-sensing devices include ultrasonic sensors mounted on the implement frame for ultrasonically detecting the height of the frame above the ground. Several of these devices can be used per frame section and can be connected to electronic circuitry for providing an average height of the implement frame. However, these devices are quite sensitive and can be adversely affected by trash flow or local soil irregularities. Electronically averaged systems require wiring harnesses connected between the sensors and the control box on the cab of the towing vehicle. To provide an accurate average over the entire width of each implement section, numerous sensors must be utilized which increases the cost and complexity of the system significantly.
It is therefore an object of the present invention to provide an improved depth-sensing arrangement for an agricultural implement.
It is a further object to provide a depth-sensing arrangement for an agricultural implement which is less costly, more accurate and less sensitive to local irregularities than at least most previously available systems. It is another object to provide such a system which accurately averages the depth of the implement over substantially its entire width.
It is a further object to provide a depth-sensing system for an agricultural implement which more accurately gauges the depth of tilled soil without the need to mount additional gauging wheels. It is a further object to provide such a system which utilizes a soil-smoothing attachment which is common to many seeding and tillage implements to thereby minimize the amount of additional hardware which must be attached to the principal tillage or seeding implement frame.
It is still another object of the present invention to provide a height-sensing device which requires only a single sensor to provide an indication of the overall average of the distance of a tillage implement above the ground. It is a further object to provide such a sensor which can be utilized on each section of a multiple-section implement to independently regulate the depth of penetration of the tools on each implement section.
It is another object of the present invention to provide a depth-sensing arrangement for an agricultural implement which effectively utilizes a soil-leveling or smoothing implement such as a spring-tine harrow or rolling-basket harrow to provide an average depth indication over a substantial portion of the width of the implement. It is another object to provide such an arrangement which averages over a large area of tilled soil.
In accordance with the above objects, a smoothing implement such as a spring-tine harrow, a rolling-basket harrow or a press wheel gang is pivotally connected to the rear portion of the tool-carrying frame of a planting or tillage implement. The depth of penetration of the tools is dependent upon the height of the implement frame above the ground, and as this height changes, the smoothing tool will rock about its pivotal connection with the main frame. The angle between the main frame and the trailing implement provides an indication of the depth of penetration of the tools. A hydraulic or electrohydraulic actuator utilizes the indication of the angle between the trailing tool and the main frame to control the wheel lift cylinders to maintain the implement frame and thus the tillage tools at a preselected operating depth. In one embodiment, where three or more fore-and-aft extending arms are pivotally connected to the main frame to tow the trailing implement, the sensor is positioned on the central-most arm to provide an averaging effect. In another embodiment, where only two arms are necessary to tow a narrower trailing implement, a transverse member is connected to the arms and the sensor is operably connected to a central portion of the transverse member to provide the averaging effect across the two arms. When a multi-section implement is utilized, a separate sensor is provided for each section to individually control the respective hydraulic cylinder or cylinders to adjust the depth of that section.
The cost and complexity of the depth-sensing system is reduced by using the existing components on a tillage or planting system. An accurate indication of depth is provided by averaging the depth of tilled soil over a substantial portion of the width of the implement. Local irregularities are absorbed by the individual elements of the smoothing attachment. By utilizing a trailing smoothing implement to sense depth, depth can be controlled relative to the final soil surface, which is particularly useful with planting and seeding equipment. The rear mounted system also prevents the controlled implement from dropping too deeply when crossing a swale.
These and other objects, features and advantages of the present invention will become apparent to those skilled in the art from the description which follows and from the drawings.